/*
 * Copyright (c) 1982, 1986, 1993, 1994
 *	The Regents of the University of California.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *	This product includes software developed by the University of
 *	California, Berkeley and its contributors.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 *	@(#)uio.h	8.5 (Berkeley) 2/22/94
 */

#ifndef _SYS_UIO_H_
#define	_SYS_UIO_H_

/*
 * XXX
 * iov_base should be a void *.
 */
struct iovec {
	char	*iov_base;	/* 缓存起始地址，调用 uiomove()发生数据拷贝后，起始地址会后移最多移动iov_len长度 */
	size_t	 iov_len;	/* 缓存长度 */
};

enum	uio_rw { UIO_READ, UIO_WRITE };

/* Segment flag values. */
enum uio_seg {
	UIO_USERSPACE,		/* from user data space，用户数据空间 */
	UIO_SYSSPACE,		/* from system space，内核数据空间 */
	UIO_USERISPACE		/* from user I space，用户指令空间 */
};

#ifdef KERNEL
struct uio {
	/* 缓存数组和元素个数，uio_segflg为UIO_USERSPACE时，由struct msghdr结构的msg_iov和msg_iovlen而来 */
	struct	iovec *uio_iov;
	int	uio_iovcnt;

	enum	uio_seg uio_segflg;	/* uio_iov 数据来源，eg.UIO_USERSPACE */
	enum	uio_rw uio_rw;		/* uio_iov 数据处理方式，eg.UIO_READ */

	off_t	uio_offset;			/* 记录某次使用 uiomove()进行数据拷贝时，从uio_iov中考出或向uio_iov拷入数据的偏移量 */
	int	uio_resid;				/* 记录某次使用 uiomove()进行数据拷贝时，剩余未拷贝字节长度。未拷贝前为所有buf的总长度 */

	struct	proc *uio_procp;	/* 处理进程 */
};

/*
 * Limits
 */
#define UIO_MAXIOV	1024		/* max 1K of iov's */
#define UIO_SMALLIOV	8		/* 8 on stack, else malloc */
#endif /* KERNEL */

#ifndef	KERNEL
#include <sys/cdefs.h>

__BEGIN_DECLS
ssize_t	readv __P((int, const struct iovec *, int));
ssize_t	writev __P((int, const struct iovec *, int));
__END_DECLS
#endif /* !KERNEL */
#endif /* !_SYS_UIO_H_ */
